This invention relates generally to lighting devices, and particularly to a projector-type lighting device suitable for use as a vehicular headlamp or the like.
The projector-type headlamp has been known which comprises a light bulb and a reflector for reflecting and converging the light from the bulb. Also included is a plano-convex projection lens having a focus in the vicinity of a point or line of convergence of the reflected light. When the light bulb is lit up, the headlamp projects a coherent light beam of very sharply delineated outline. The projector-type lamp is well suited for vehicular headlamp applications by virtue of its capability of meeting the most stringent beam pattern standards.
A drawback has existed with the prior art projector-type headlamp, however. The current trend in the design of vehicle headlamps is toward larger size, particularly a greater horizontal dimension in comparison with a vertical dimension. Automobile designers have objected to the projector-type headlamp by reasons of its compactness and the round shape of the projection lens.
In order to overcome this weakness, it has been suggested to install a projector-type light source assembly, comprised of a light bulb, a reflector and a projection lens, within a lamp housing or body of much larger size and esthetically appearing shape. An annular reflector is mounted in the space left within the lamp housing by the light source assembly. The light source assembly projects a light beam through the central aperture in the annular reflector in the nighttime. In the daytime, as the reflector reflects the daylight, the headlamp appears much larger than the projector-type light source assembly, the latter being practically invisible.
This known solution is objectionable because the reflector is mostly invisible in the nighttime. Only the projector-type light source assembly appears bright. Consequently, as the car with a pair of such headlamps travels, it may hallucinate the pedestrians and the drivers of the meeting and preceding vehicles into the wrong perception that two motorcycles are running side by side. The wrong perception may invite wrong traffic decisions by the pedestrians and the drivers, possibly resulting in traffic accidents in the worst case.